Lightly score the snapper with a sharp knife in a diamond pattern on both sides. Brush with oil inside and out and sprinkle with salt and pepper. Rub the ginger into the cuts.
Place the fish on sheets of heavy duty aluminium foil. Place a sprig of bay leaves in the cavity and lay the lemon slices over the uppermost side of the fish. Wrap the fish securely in the foil, sealing the edges tightly.
Place the fish on the barbecue and cook 20 minutes. Turn the fish and cook 20 minutes more.